Design Basis Threat (DBT)

A fundamental principle of physical protection is that it should be based on the State’s current
evaluation of the threat. This evaluation is formalized through a Threat Assessment process. A
DBT is derived from this threat assessment. To define the DBT, the set of threat described in the
State’s Threat Assessment are refined to take account of other issues (for example technical,
economic, and political issues) and the particular requirements of planning for system design. To
make the transformation from Threat Assessment to DBT, rigorous analysis and decision-making
are essential.

IAEA publication INFCIRC/225/Rev.4 (Recommendations for Physical Protection of Nuclear
materials and Nuclear Facilities) states that a DBT is a description of the attributes and
characteristics of potential insider and/or external adversaries who might attempt unauthorized
removal of nuclear material or sabotage against which a physical protection system is designed
and evaluated.

The definition of a DBT contains four important themes. These are:

Insider and/or external adversaries – A potential adversary is any individual or group of
individuals deemed to have the intent and/or the capabilities to conduct a malicious act.

Malicious acts leading to unacceptable consequences – Measures need to be taken to prevent
malicious acts, such as unauthorized removal of material or sabotage, and protect against their
unacceptable consequences.

Attributes and characteristics – The attributes and characteristics of potential adversaries describe
their capabilities to carry out a malicious act. Capabilities may include weapons, explosives,
tools, transportation, insiders and insider collusion, skills, actics, and number of individuals. These capabilities help determine the detection, delay, and response criteria for design and
evaluation of an effective physical protection system.

Design and evaluation – A DBT, which is defined at the State level, is a tool used to help establish
performance requirements for the design of physical protection systems. A DBT is also used to
help Operators and the State authorities assess the effectiveness of the systems to counter
adversaries by evaluating the systems’ performances against their capabilities described in the
DBT.

The DBT outlines the set of adversary characteristics for which the Operators and State
organizations together have protection responsibility and accountability. The division of these
responsibilities may vary according to States. The DBT is used to define the requirements given to
the Operators and to clarify the protection functions that are the responsibilities of the State's
Authorities.

It is important to recognize that the specific capabilities contained in a DBT are independent of
which organizations (Operator alone, State and Operator together, or Operator in association with
another organisation) are intended to use it. A State may desire to have more than one DBT
either to reflect the various targets (for example, nuclear and radioactive materials) and protection
needs among different types of materials, or according to different types of facilities (for example,
power plants and research reactors), different adversary objectives (for example, theft, sabotage,
economic disruption), or different geographic regions. This distinction highlights the importance
of clarifying the planned use of a DBT prior to developing it.

Need for the DBT

A physical protection system has a specific objective: to prevent adversaries from successfully
completing a malicious act and thereby achieving their purpose. A clear description of this threat
is an essential prerequisite for assured and effective physical protection. Ideally, intelligence
would provide sufficient information for the specification of design and performance requirements
for a physical protection system to help ensure that this objective is met. However, intelligence is
often limited, and threats are inherently dynamic. A physical protection system designed only for
the today’s threat may not be effective against tomorrow’s threat.

In the absence of a sufficiently detailed and accurate description of the threat, it is difficult to
determine with precision the amount of protection that would be appropriate and effective for a
given facility or activity in order to prevent unacceptable consequences from an adversary. Given
the potentially severe consequences of some malicious acts and the high costs of providing
protection, uncertainties about the threat are unlikely to be acceptable to State authorities who are
responsible for deciding how much protection is appropriate. Without a well-specified description
of the threat, it may be very difficult to determine with confidence whether protection is adequate
and sufficient.

In order to address the need for a well-specified description of the threat, the concept of a DBT
was introduced. A DBT is the State’s description of a representative set of attributes and
characteristics of adversaries, based upon (but not necessarily limited to) a State’s Threat
Assessment that the State has decided to use as a basis for physical protection system design and evaluation.

Value of a DBT

The DBT provides a basis for confidence that the protection system developed is appropriate and
effective. It provides both a basis for system design and a consistent criterion for assessing the
adequacy of a physical protection system. It also provides a baseline standard against which the
need for changes in physical protection can be evaluated. The DBT can permit the customization
of the physical protection systems to address unique features of the materials or facilities. It can
help avoid excessive protection being applied to facilities and materials while ensuring that
facilities and materials for which a malicious act could result in high consequences get the
protection they require. In this manner, the use of the DBT approach to physical protection can
help to reduce the arbitrariness that might otherwise exist in establishing requirements for the
physical protection of material and facilities under State jurisdiction. Finally, it also provides a
clear basis for allocating responsibility between involved organizations.

A DBT is not an end in itself but rather a tool for achieving a set of objectives. Adopting a DBT
approach to regulation of physical protection of material and facilities under a State’s jurisdiction
is only of value to the State if it is used to design and assess physical protection. To accomplish
this, the approach needs to be incorporated into the regulatory framework and used to:

establish objectives and requirements for physical protection systems

determine physical protection system design

establish criteria for physical protection system evaluation

identify protection functions that are the responsibility of the State.

At the Operator level, methods of detection, measures for delay, and the composition of the
response to malicious acts should be developed to address the adversary capabilities described in
the DBT. In short, the physical protection system, and each of the measures that comprise the
system, should be developed in the light of, and assessed against, the DBT.